Human Origins is full of unsolved mysteries. Sometime after 100,000 years ago, for example, humans went from being limited to particular regions to rapidly colonizing the whole world, and we have been unable to explain quite why. People spread ‘against the odds’ – moving quickly out of Africa, at around 1km per year, crossing daunting barriers like major deserts, spreading from the north to the very south of the Americas and even across at least 60km of sea to Australia. They cannot have had any concept of going somewhere, there is no evidence that population increase forced them to move, and they took substantial, some might say nonsensical, risks. Bar-Yosef and Belfer-Cohen have said of this dispersion ‘.. the easiest questions to resolve are those of ‘when’ and ‘how’ while the most difficult and the most highly debated is ‘why’’.
My research has provided a possible explanation. The significance of the gradual evolution of capacities for social emotions – such as compassion, sympathy, remorse or darker feelings of spite and revenge – to human behavior seems to have been overlooked. Through time we have become over more closely bound to those we care about, but yet ever more affected by cheating or betrayals of trust, feeling so strongly both about those we love, and those we hate, that we can be motivated to behave in completely irrational ways. When we understand the significance of our social emotions to have we behave, we can see why someone intent on revenge might spur most of us onto on the open sea in even the flimsiest of rafts to get out of harm’s way.
By looking at evidence for the dynamics of emotional commitments and why modern hunter-gatherers fall out, find allies and move somewhere new, we can see that rather than our intellect it may have been the evolution of our complex emotional lives which provides the best explanation for our global expansion.